1. Field of the Invention
The present invention, in general relates to braking systems and braking methods for cargo portage devices and more particularly, to braking systems and braking methods for use with wheelbarrows comprising a cargo receptacle mounted to two handles that project forward beyond the front of the cargo receptacle and rearward beyond the rear of the cargo receptacle. The forward handle projections enable mounting at least one front wheel that facilitates movement of the device. The rear handle projections have hand grip ends that a user can grasp to raise or lower the rearward portion of the wheelbarrow to facilitate controlling the movement and direction of the device. To further describe such wheelbarrows, they usually have wheels or struts placed underneath and towards the rear of the cargo receptacle to enable the wheelbarrow to stand upright when it is at rest unsupported by a user.
Further, the handles of such wheelbarrows have a nominal length of approximately 60 inches and the rear, gripping ends of the handles rest at a nominal height of approximately 20 inches above the surface on which the wheelbarrow rests while unsupported by its user, and the nominal distance from the hand-grip ends of the handles to the point at which the rear support of the wheelbarrow sits on a surface is approximately 36 inches. These parameters have been mentioned to clearly distinguish the types of portage devices to which my present braking system applies from other cargo portage devices, such as carts of various designs. For descriptive purposes, the portage devices I have described will be referred to as “conventional” wheelbarrows throughout this patent application to assist in teaching what's different about the construction and method of using my present braking system for a cargo portage device.
2. Description of Prior Art
There is a multitude of designs of wheelbarrows known in the prior art. One commonality among conventional wheelbarrows is that, owing to the method by which they are used, they all typically have only one fulcrum of useful leverage. The advantage of this leverage is realized when the axle of the front wheel(s) is used as a fulcrum in conjunction with the user raising the rear ends of the handles of the wheelbarrow to lift its load for transporting.
Conventional wheelbarrows perform well when being pulled or pushed over a surface that has no obstructions of significant height, relative to the diameter of their front wheel(s), in their path of travel. Typical obstructions could be curbs, logs, stones or steps, for example. When a user pushing a conventional wheelbarrow confronts such an obstruction and can't move around it, he or she can sometimes traverse the obstruction by “ramming” into it with the front wheel(s) of the wheelbarrow and bouncing up over it if the obstruction is no more than about three inches high. This often leads to the wheelbarrow tipping over, causing it to spill its load. An equally devastating consequence can occur if the wheelbarrow is being used, in the manner just described, to transport fragile cargo over an obstruction even if the wheelbarrow doesn't tip over.
When a user of a conventional wheelbarrow determines that it is either unwise or impossible to push or ram the wheelbarrow over an obstruction, he or she will usually make the choice of turning the wheelbarrow around and pulling it up over the obstruction. When this becomes necessary, the user of such a wheelbarrow has to exert enough force to overcome two sources of resistance: 1) The obstruction that the user is trying to traverse with the wheelbarrow presents a virtually infinite source of resistance to progress of the wheelbarrow in the desired direction of travel, and 2) The force of gravity provides resistance working downwardly against the mass of the wheelbarrow and its cargo. Because of this, the user has to lift the weight of both the wheelbarrow and its cargo upward over the obstruction, while standing in a posture that is disadvantageous for lifting.
In the situations just mentioned, conventional wheelbarrows not only lose part of the utility of their valuable assets, they are also an impediment to their users, because their users have to exert enough upward force to haul the weight of both the wheelbarrow and its cargo over the obstruction without the advantage of leverage. It is only after a user has suffered the stress of exerting this unleveraged force to get the wheelbarrow over the obstruction that the advantages of such a wheelbarrow again become apparent.
Known conventional wheelbarrows have two fulcrums of leverage. The axle of the front wheel(s) is the fulcrum of leverage when the user lifts the rear of the wheelbarrow's handles in order to raise its load of cargo to the transporting position. This is useful leverage and is partly what has made the wheelbarrow the important tool that it is. Some conventional wheelbarrows have struts that are usually located underneath and towards the rear of the cargo receptacle. The second fulcrum of leverage for such wheelbarrows is constituted by the bottom of their struts. This leverage comes into play when the user pushes down on the rear of the wheelbarrow's handles causing the wheelbarrow's front end to rise. Although this leverage facilitates raising the front end of the wheelbarrow, it is usually useless leverage, because it removes the wheelbarrow's front wheel(s) off the surface and this puts it in a situation in which it can't be easily moved, thus impeding the transport of its load. The wheelbarrow can't be easily moved when in this position, because removing its front wheel(s) from the surface transfers the combined forces of the wheelbarrow's weight, the weight of its cargo and the force of the user pushing down onto the relatively immovable struts, which are usually going to be sitting on a surface that has a relatively high coefficient of sliding friction. Since wheelbarrows are designed to transport loads; employing the use of one or more wheels; either horizontally or up or down an incline, little value can be realized from using their leverage to move their front wheel(s) vertically off a surface.
A further limitation of strut-fitted conventional wheelbarrows is that they have no provisions for using them to move an extremely heavy load, such as when the weight of the load exceeds the load carrying capacity of the front wheel(s) or when more than one person is needed to use the wheelbarrow to move a load up a steep incline. Some wheelbarrow designers have attempted to overcome this limitation by adding wheels underneath and towards the rear of the cargo receptacle in place of the struts. Such attempts have often revealed other design shortcomings, such as the lack of adequate brakes that could prevent unwanted movement of the wheelbarrow.
Some examples of disadvantages resulting from the lack of adequate brakes in known conventional wheelbarrows of this type are: 1) Requiring that the device be pulled by a towing vehicle which would provide the braking; 2) having no brakes at all; and 3) brakes that either cannot be firmly locked in both the “On” and the “Off” positions or brakes that do not default to the “On” position without user intervention. This latter feature is an important safety feature for the common situations in which a user is likely to forget to lock the brakes or children are likely to use the wheelbarrow as a riding toy and roll it down an incline.
Although a variety of improvements and adaptations of wheelbarrow brakes are known, none include the novel combination of features or employ the method of use that would enable them to be used in the manner that will be described for the present wheelbarrow braking system and none of them singularity employ the embodiments that lend themselves to the use of my new methodology. My present wheelbarrow braking system and its method of use relies on applying a frictional force to the tread of wheels positioned underneath and towards the rear of the wheelbarrow's cargo receptacle. Wheelbarrows employing brake systems to wheels positioned underneath and towards the rear of the wheelbarrow's cargo receptacle are known in the prior art, but their design fails to enable those wheelbarrows to be used in the manner that wheelbarrows can be used when they are fitted with my present wheelbarrow braking system. I will mention three such inventions below, but it is to be understood that my mentioning them is solely for the purpose of objectively teaching how their designs fail to lend themselves to the use of my new method and not for the purpose of disparaging them.
The first two of those three inventions employ brakes that control the rotation of wheels mounted on swivel casters. In general, the operation of the braking system for my new method of use won't function properly on wheels mounted on swivel casters, since the wheels need to be mounted pointed in a fixed direction in a plane parallel to or coincident with the longitudinal centerline of the wheelbarrow on which my new brake system is installed.
One invention is U.S. Pat. No. 6,220,622 to Garcia, issued Apr. 24, 2001. This invention discloses the use of large swivel casters for its two rear wheels. It claims that the swivel feature of the casters is to be offset from the vertical centerline of the swivel's spindle so that the wheels can “trail”, very much like offset casters on an office chair. While swivel casters may likely keep the wheelbarrow standing upright when all three of its wheels are on a resting surface, the wheelbarrow is likely to tip over if it is allowed to rest on only the two rear swivel casters in the manner that will be described for using the present invention. This is because the invention fails to teach how to provide for positioning the casters so that they simultaneously point in the same direction. This condition can be simulated by leaning an office chair back so that it rests on two of its casters, turning the toe of one caster in one direction, then turning the toe of the other caster in another direction and watching the tilting of the back of the chair. The larger the casters are, the more pronounced this tilting will be. Casters used on an office chair, as described above, are much smaller than those that would be used on a wheelbarrow because of the nature of the surface that a wheelbarrow is often used on, e.g., dirt, unsmooth surfaces, etc.
If the hinged braking mechanism of this invention is installed as shown in FIG. 4 of the disclosure, it wouldn't take a great deal of backward motion of the wheelbarrow (such as from throwing an object into it, rather than gently lying it in place) for the brakes to be jarred out of the locked position—especially since the brake is already biased towards the unlocked position by the coil spring 64 shown in that disclosure.
A second invention using two rear wheels and a gravity operated parking brake is U.S. Pat. No. 4,767,128 to Terhune, issued Aug. 30, 1988. This invention also discloses the use of large swivel casters for the two rear wheels. The invention doesn't teach whether the swivel casters have offset or straight spindles. If the casters are offset, they will contribute to the problem of the wheelbarrow tipping over as was described in the Garcia invention mentioned above. If the swivel casters are straight, the wheelbarrow would be practically impossible to steer if it were riding on its two rear wheels or on all three wheels. This is because straight swivel casters have no “trailing” ability unless some mechanical embodiments, not shown in this invention, are added to cause the casters to point in the desired direction.
It is possible to lock the brakes on this wheelbarrow in the disengaged position, which could cause the wheelbarrow to run away on its own down an incline should the user forget to put the brakes in the engaged position.
A third invention is shown in U.S. Patent Office Publication No. 2003/0015852 A1, published Jan. 23, 2003. That invention, which is the product of this inventor, discloses a wheelbarrow with dual rear wheels and a parking brake. The brakes on this wheelbarrow can be locked in either the “On” the “Off” state. It does not provide for the brakes to default to the “On” state if the user forgets to consciously lock them. This invention is currently still being prosecuted under a Request For Continued Examination.